IC socket, a test method using the same and an IC socket mounting mechanism

ABSTRACT

An IC to be tested having solder bumps is mounted on an IC socket mounted on a test board. The IC socket is provided with a contact unit including a plurality of straight contact pins each having an lower end connected to the test board and an upper end connected to the solder bumps and also including an elastic member for supporting the plurality of contact pins. A diameter of the plurality of contact pins is configured to be sufficiently small for the plurality of contact pins to pierce the respective solder bumps so that an electrical connection is established by the upper end of each of the plurality of solder bumps piercing an associated one of the solder bumps.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to IC sockets, test methods usingthe same and IC socket mounting mechanisms, and more particularly, to anIC socket for testing a semiconductor device (IC) having projectionelectrodes formed as bumps or the like, a test method using such an ICsocket and a mechanism for mounting such an IC socket.

[0003] Many of the ICs used recently are constructed to have projectionelectrodes formed as solder bumps for connection with an externaldevice, for the purpose of reducing the size of a package. For example,a ball grid array (BGA) has such a construction. Demands forhigh-density, high-speed semiconductor devices having projectionelectrodes are growing for further reduction in the package size.Associated with this, pitch between electrodes is on a decreasing trend;and projection electrodes are being arranged with an increasingly higherdensity and on an increasingly reduced scale.

[0004] Once produced, the ICs are subject to a performance test to seeif a prescribed performance is provided. The ICs are tested by beingmounted on an IC socket. Therefore, the IC socket should be adapted forthe high-density, small-scale trend of the ICs. As a result of thehigh-density, small-scale trend, the strength of each projectionelectrode has become extremely low so that it is necessary to ensurethat the projection electrodes are not damaged when brought into contactwith contact pins provided in the IC socket.

[0005] 2. Description of the Related Art

[0006] FIGS. 1-5 show a construction of a conventional IC socket 1. Asshown in FIGS. 1-3, the IC socket 1 generally comprises a socket body 2,a lid 3, contact pins 4 and a substrate 5. The IC socket 1 is designedso that an IC 7 of a BGA type provided with solder bumps 6 (projectionelectrodes) is mounted on the IC socket 1 and tested for itsperformance.

[0007] The socket body 2 includes a cavity 8 in which the substrate 5 isfitted. The cavity 8 is provided with through holes 9 aligned with thesolder bumps 6 formed in the IC 7. The substrate 5 is provided withmounting holes 10 also aligned with the solder bumps 6 formed in the IC7.

[0008] The contact pins 4 are formed by punching a thin metal plate soas to have a crooked configuration that provides a spring action asshown in FIGS. 2 and 3. The contact pins 4 have contact parts 4 a,formed at the upper end thereof, inserted into mounting holes 10 of thesubstrate 5. Terminal parts 4 b formed at the lower end the contact pins4 are inserted into the through holes 9 formed in the cavity 8 and aremade to project from the bottom of the socket body 2. The same number ofthe crooked contact pins 4 is provided as the number of solder bumps 6formed in the IC 7. The contact pins 4 are designed to remainpress-fitted into the through holes 9 and the mounting holes 10 whilebeing accommodated in the IC socket 1.

[0009] The lid 3 is rotatably fitted to the socket body 2 by a pivotpart 11. By closing the lid 3 when the IC 7 has been mounted on thesocket body 2, the lid 3 presses the IC 7 toward the substrate 5. As aresult, the bumps 6 formed in the IC 7 are pressed against the contactparts 4 a of the contact pins 4. The contact pins 4 are elasticallydeformed so as to press the solder bumps 6 by the elastic action.Accordingly, the contact pins 4 and the solder bumps 6 are electricallyconnected. A lock lever 12 is provided in a lid 3. The lock lever 12locks the lid 3 in the closed position.

[0010] The IC socket 1 having the above-described construction isdesigned to be mounted on a test board 13 by a solder reflow process orthe like after the terminal parts 4 b projecting from the underside ofthe socket body 2 are inserted into through holes 14 formed in the testboard 13. The test board 13 is connected to a test device (for example,a burn-in test device) for performing a test of the IC 7. Thus, aprescribed test is performed on the IC 7 mounted on the IC socket 1 viathe test board 13.

[0011] It is known that a thin oxide film 15 (see FIG. 5) is formed onthe surface of the solder bumps 6 formed in the IC 7. Since the oxidefilm 15 has a low conductivity, it is necessary to penetrate the oxidefilm 15 in order to establish an electrical connection between thesolder bumps 6 and the contact pins 4.

[0012] Conventionally, as shown in FIG. 4 showing the part A indicatedby the arrow in FIG. 3 on an enlarged scale, the elastic deformation ofthe contact pins 4 occurring when the lid 3 is closed is utilized. Morespecifically, it is expected that the elastic deformation causes thecontact parts 4 a of the contact pins 4 to be displaced in the directionindicated by the arrow of FIG. 4 so that the contact parts 4 a slide onthe surface of the solder bumps 6 such that the contact parts 4 apenetrate the oxide film 15.

[0013] With the increasingly smaller solder bumps 6 provided on the IC 7recently, the strength of the solder bumps 6 has decreased. Accordingly,the method whereby the contact parts 4 a are expected to penetrate theoxide film 15 by sliding on the surface of the solder bumps 6 produces adeformation in the solder bump 6 while the contact parts 4 a slide onthe surface thereof. The deformation of the solder bumps is indicated bythe arrow 6 a of FIG. 5. If any of the solder bumps 6 is deformed, avariation in the height of the solder bumps 6 occurs when the IC 7 ismounted on a circuit board or the like after the test. The solder bumps6 may not be properly mounted on the circuit board.

[0014] In the conventional IC socket 1, a high level of precision isrequired to provide the contact pins 4 having a crooked configurationthat provides a spring action in the socket body 2. The press-fitting ofthe crooked contact pins 4 demands intensive attention. Another problemsis that, as the size of the contact pins 4 become smaller with thereduction in the size of the solder bumps 6, it is increasinglydifficult to produce the contact pins 4 having a complex crookedconfiguration, and the cost of the production increases accordingly.

SUMMARY OF THE INVENTION

[0015] Accordingly, it is an object of the present invention to providean IC socket, a test method using the same and an IC socket mountingmechanism.

[0016] Another and more specific object of the present invention is toprovide an IC socket, capable of performing high-precision testingwithout damaging small projection electrodes, a test method using suchan IC socket and an IC socket mounting mechanism for mounting such an ICsocket.

[0017] In order to attain the aforementioned objects, the presentinvention provides an IC socket mounted on a test board while in use andhaving a semiconductor device with projection electrodes mounted on saidIC socket for testing, said IC socket is constructed such that adiameter of a plurality of straight contact pins having a first endelectrically connected to said test board and a second end thereofconnected to said projection electrodes is sufficiently small for eachof said plurality of contact pins to pierce said projection electrodes,said IC socket being electrically connected to said test board by saidfirst end of said plurality of contact pins piercing said projectionelectrodes.

[0018] According to the IC socket of the present invention describedabove, one end of each of the contact pins constituting the contact unitis electrically connected to a test board and the other end is connectedto the projection electrodes. Thus, an electrical connection is properlyestablished between the projection electrodes and the test board.

[0019] By configuring the diameter of the contact pin to be small enoughfor the contact pin to pierce the projection electrode for an electricalconnection therewith, it is ensured that, even if an insulating filmsuch as an oxide film is created on the projection electrode, thecontact pin can be electrically connected to the projection electrode bypenetrating the insulating film.

[0020] Since the contact pin has a significantly small diameter, theprojection electrode is not deformed, only a fine hole being created inthe projection electrode when pierced by the contact pin. Thus, ahigh-precision mounting of an IC is possible.

[0021] Even with its fine diameter, it is highly unlikely that thecontact pin is bent or curved because the contact pins are supported bythe supporting structure constituting the contact unit. Therefore, anelectrical connection is properly established between the contact pinand the projection electrode.

[0022] The aforementioned objects may also be attained by an IC socketmounted on a test board while in use and having a semiconductor devicewith projection electrodes mounted on said IC socket for testing, saidIC socket comprising: a plurality of straight contact pins having afirst end electrically connected to said test board and a second endconnected to said projection electrodes; and a supporting structure forsupporting said plurality of contact pins, each of said plurality ofcontact pins provided at the second end with a deformable partdeformable according to a pressure occurring between said contact pinand an associated one of said projection electrodes.

[0023] According to the IC socket according to the present inventiondescribed above, deformation of the deformable part provided at thatportion of the contact pin which is connected with the projectionelectrode cancels a variation in the height of the projection electrodesor a variation in the pressure caused by an irregularity on the surfaceof the test board. Since the deformable part is deformed in conformityto the configuration of the projection electrodes, a relatively largecontact area is secured. Thus, the deformable part is suitable forimproving an electrical conductivity between the contact pins and theprojection electrodes.

[0024] Even when the projection electrodes are formed of a soft metalsuch as a solder, the pressure applied to the projection electrodes isrelatively small as a result of the deformable part being deformed.Accordingly, an electrical connection can be properly establishedbetween the contact pins and the projection electrodes without causingdamage in the projection electrodes.

[0025] The aforementioned objects may also be attained by an IC socketmounting mechanism for mounting, on a test board, an IC socketcomprising a contact unit having a plurality of straight contact pinsfor electrically connecting the test board and projection electrodes ofa semiconductor device and also having a supporting structure forsupporting said plurality of contact pins, the test board included insaid IC socket mounting mechanism being provided with through holes towhich said plurality of contact pins are electrically connected, andeach of said plurality of contact pins having one end thereof connectedto said test board and provided with an elastically deformable part sothat an elastic resilient force generated when said elasticallydeformable part is inserted in an associated one of said through holescauses said contact pin to be pressed against the through hole and toestablish an electrical connection therewith.

[0026] According to the IC socket mounting mechanism of the presentinvention, a relatively simple operation of inserting the elasticallydeformable part into the through hole ensures that an electricalconnection is established between the contact pins and the test board.Since the elastically deformable part in the through hole presses thethrough hole by an elastic resilient force, an improved electricalconnection between the contact pins and the test board is established.

[0027] The present invention also provides an IC socket mountingmechanism for mounting, on a test board, an IC socket comprising acontact unit having a plurality of straight contact pins forelectrically connecting the test board and projection electrodes of asemiconductor device and also having a supporting structure forsupporting the plurality of contact pins, the test board included in theIC socket mounting mechanism being provided with through holes at apitch greater than a pitch at which the projection electrodes arearranged, and each of the plurality of contact pins is configured to belong enough to extend from the supporting structure to reach anassociated one of the through holes formed in the test board.

[0028] According to the IC socket mounting mechanism described above,the through holes can be arrayed at a relatively wide pitch even if thepitch at which the projection electrodes are arrayed is relativelysmall. Thus, forming of the through holes becomes easier, and forming ofthe wiring pattern provided on the test board for connection with thethrough holes also becomes easier.

[0029] The aforementioned may also be attained by an IC test system fortesting a semiconductor device mounted on an IC socket which is mountedon a test board connected to a test device, the IC socket beingconstructed such that a diameter of a plurality of straight pins havinga first end electrically connected to the test board and a second endthereof connected to the projection electrodes is sufficiently small foreach of the plurality of contact pins to pierce the projectionelectrodes, the IC socket being electrically connected to the test boardby the first end of the plurality of contact pins piercing theprojection electrodes.

[0030] The present invention further provides an IC test system fortesting a semiconductor device mounted on an IC socket which is mountedon a test board connected to a test device, said IC socket comprising: aplurality of straight contact pins having a first end electricallyconnected to said test board and another end connected to saidprojection electrodes; and a supporting structure for supporting saidplurality of contact pins, each of said plurality of contact pinsprovided at the second end with a deformable part deformable accordingto a pressure occurring between said contact pin and an associated oneof said projection electrodes.

[0031] According to the IC test system of the present invention, thereliability of the test on a semiconductor device can be improvedbecause an electrical connection between the projection electrodes ofthe semiconductor device and the contact pins of the IC socket can beproperly established.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Other objects and further features of the present invention willbe apparent from the following detailed description when read inconjunction with the accompanying drawings, in which:

[0033]FIG. 1 is a perspective view of a conventional IC socket;

[0034]FIG. 2 is an exploded perspective view of the conventional ICsocket;

[0035]FIG. 3 is a sectional view of the conventional IC socket;

[0036]FIG. 4 is an enlarged view of a portion of FIG. 3;

[0037]FIG. 5 illustrates a problem with the conventional IC socket;

[0038]FIG. 6 shows a basic construction of an IC socket according to thepresent invention;

[0039]FIG. 7 is a schematic illustration of a construction of the ICsocket according to a first embodiment of the present invention;

[0040]FIG. 8 is a partial enlarged view of the IC socket according tothe first embodiment before an IC is mounted on the IC socket;

[0041]FIG. 9 is a partial enlarged view of the IC socket according tothe first embodiment after the IC is mounted on the IC socket;

[0042]FIG. 10 is a schematic view of an IC socket according to a secondembodiment of the present invention;

[0043]FIG. 11 is an enlarged view of a part indicated by the arrow B ofFIG. 10;

[0044]FIG. 12 is an enlarged view of a part indicated by the arrow C ofFIG. 10;

[0045]FIG. 13A shows how an IC is positioned in the supportingstructure;

[0046]FIG. 13B is a partial enlarged view of FIG. 13A;

[0047]FIG. 14A shows how an IC is positioned in the supportingstructure;

[0048]FIG. 14B is a partial enlarged view of FIG. 14A;

[0049]FIG. 15 is a partial enlarged view of an IC socket according to athird embodiment of the present invention;

[0050]FIG. 16 is a bottom view of a guide plate provided in the ICsocket according to the third embodiment;

[0051]FIG. 17 is a partial enlarged view of an IC socket according to afourth embodiment of the present invention;

[0052]FIG. 18 is a partial enlarged view showing an operation of the ICsocket according to the fourth embodiment of the present invention;

[0053]FIG. 19 is a partial enlarged view of an IC socket according to afifth embodiment of the present invention;

[0054] FIGS. 20A-20C show configurations of an upper end of a contactpin;

[0055]FIGS. 21A and 21B show configurations of an upper end of a contactpin;

[0056]FIGS. 22A and 22B show configurations of an upper end of a contactpin;

[0057] FIGS. 23A-23C show configurations of an upper end of a contactpin;

[0058] FIGS. 24A-24C show variations of an IC socket mounting mechanism;and

[0059]FIG. 25 shows how a contact pin is connected to a test board.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0060]FIG. 6 shows a basic construction of an IC socket 200 according tothe present invention. Referring to FIG. 6, the IC socket 200 comprisesa socket body 21, a lid 22 and contact pins 30. The IC socket 200accommodates a semiconductor device 25 (IC) of a BGA type provided withprojection electrodes 28 so as to test the IC 25.

[0061] While the description given below assumes that the projectionelectrodes are embodied by solder bumps, the present invention may beapplied to other types of projection electrodes. More specifically, thepresent invention may be applied to ICs having wire bumps, bumps formedby plating, etc.

[0062] The socket body 21 is formed of a molded resin. A cavity 26 isformed inside the socket body 21. The contact pins 30 are arrayed in thecavity 26.

[0063] The lid 22 is pivotably fitted to the socket body 21 by a pivotpart 27. When the lid 22 is closed after the IC 25 is mounted on thesocket body 21, the lid 22 acts to press the IC 25 toward the contactpins 30. Accordingly, the solder bumps 28 formed in the IC 25 arepressed against the contact pins 30 so that the contact pins 30 areelectrically connected to the solder bumps 28. The lid 22 is providedwith a lock lever 29 for causing the lid 22 to be locked in a closedposition.

[0064] The IC socket 200 having the above described construction ismounted on a test board 32 connected to a test device (for example, aburn-in test device) for testing the IC 25. More specifically, IC socket200 is mounted on the test board 32 such that the contact pins 30projecting from the underside of the socket body 21 are pressed againstland parts 33 formed on the test board 32. Thus, the lower ends of thecontact pins 30 are electrically connected to the land parts 33. The ICsocket 200 may be secured to the test board 32 by an adhesive or byscrews.

[0065] In the above-described construction, the contact pins 30 areembodied by metal wires instead of being formed by punching a thin plateas is done in the conventional IC socket. Another point of note is thatthe contact pins 30 have a straight configuration instead of theconventional crooked configuration. Since the contact pins 30 arestraight, the contact pins 30 can be formed by cutting metal wires in apredetermined length. Since such a process does not require a die, thecost of production can also be reduced.

[0066] It is necessary for the contact pins 30 to be harder than thesolder bumps 28 formed in the IC 25 and to provide a certain springaction as described later. The contact pins 30 may preferably be formedof a tungsten that provides a good spring action or a beryllium copperhaving a favorable electric characteristic.

[0067] The diameter (L1) of the contact pins 30 is designed to be⅕-{fraction (1/10)} of the diameter (L2) of the solder bumps 28(projection electrodes) (L1/L2={fraction (1/5)}-{fraction (1/10)}). Morespecifically, when the diameter L2 of the solder bumps 28 is 500 μm, thediameter L1 of the contact pins 30 is set in the range of 100-50 μm.Thus, the contact pins 30 of the IC socket 200 have a significantlysmaller diameter than the diameter of the solder bumps 28.

[0068] A description will now be given of the operation and function ofthe IC socket 200 having the above construction. The IC 25 is mounted onthe IC socket 200 by being fitted inside the cavity 26 of the socketbody 21. When the IC 25 is fitted inside the cavity 26, the lid 22 isclosed and secured to the closed position by the lock lever 29. Once theIC 25 is mounted on the IC socket 200, the IC 25 is pressed hard towardthe contact pins 30.

[0069] As has been described above, the contact pins 30 are formed of amaterial harder than the material forming the solder bumps 28. Moreover,the diameter L1 of the contact pins 30 is configured to be significantlysmaller than the diameter L2 of the solder bumps 28 such that L1 is⅕-{fraction (1/10)} of L2. Accordingly, the upper ends of the contactpins 30 pierce the solder bumps 28 as the IC 25 is pressed against thecontact pins 30. Consequently, an electrical connection is establishedbetween the contact pins 30 and the solder bumps 28.

[0070] The surface of the solder bumps 28 usually has an insulating film(oxide film) 34 formed thereon. By the contact pins 30 piercing theinsulating film 34, the contact pins 30 can properly establish anelectric connection with the solder bumps 28.

[0071] Since the diameter of the contact pins 30 is significantly smallas described already, only a small hole is created in the solder bumps28 when the contact pins 30 pierce the solder bumps 38. The solder bumps28 are not substantially deformed to the extent that a variation in theheight of the adjacent solder bumps 28 results. Accordingly, the IC 25can be mounted on the circuit board with high precision after the test.

[0072] A description will now be given of specific embodiments of thepresent invention featuring the basic construction described above.FIGS. 7-9 show an IC socket 20 according to a first embodiment of thepresent invention. In FIGS. 7-9, those components that correspond to thecomponents of the IC socket 200 shown in FIG. 6 are designated by thesame reference numerals.

[0073] As shown in FIGS. 7-9, the IC socket 20 comprises the socket body21, the lid 22 and a contact unit 23.

[0074] The socket body 21 is formed of a molded resin and the cavity 26is formed inside the socket body 21. The contact unit 23 is designed tobe fitted in the cavity 26. As shown in FIGS. 7-9, the first embodimentfeatures the contact unit 23 which is separate from the socket body 21so that the construction and the constituting material of the contactunit 23 and the socket 21 may be adapted for the respective requiredfunctions.

[0075] The cavity 26 is provided with a holding mechanism (not shown)for holding the contact unit 23. The holding mechanism secures thecontact unit 23 in the socket body 21. The lid 22 is pivotably fitted tothe socket body 21 by the pivot part 27. When the lid 22 is closed afterthe IC 25 is mounted on the socket body 21, the lid 22 presses the IC 25toward the contact unit 23.

[0076] Accordingly, the solder bumps 28 formed in the IC 25 are pressedtoward the contact unit 23 so that the contact pins 30 constituting thecontact unit 23 are electrically connected to the solder bumps 28, asdescribed later. The lock lever 29 provided in the lid 22 locks the lid22 to the closed position.

[0077] The IC socket 20 having the above described construction ismounted on the test board 32 connected to a test device (for example, aburn-in test device) for testing the IC 25. More specifically, the ICsocket 20 is mounted on the test board 32 such that the contact unit 23exposed from the underside of the socket body 21 is pressed against theland part 33 formed in the test board 32, the contact pins 30 areconnected to the land part 33.

[0078] A description will now be given of the contact unit 23, thefeature of the first embodiment. The contact unit 23 comprises thecontact pins 30 and an elastic member 31 (indicated by a sattin finishedtexture) for supporting the contact pins 30.

[0079] The contact pins 30 are formed of straight metal wires. Since thecontact pins 30 are straight, the contact pins 30 can be formed bycutting metal wires in a predetermined length. Since such a process doesnot require a die, the cost of production can also be reduced.

[0080] The contact pins 30 are formed of a material which is harder thanthe solder bumps 28 formed in the IC 25 and which provides a certainspring action described later. For example, the contact pins 30 areformed of a tungsten that provides a good spring action or a berylliumcopper having a favorable electrical characteristic.

[0081] The diameter (L1) of the contact pins 30 is set to be ⅕-{fraction(1/10)} of the diameter (L2) of the solder bumps 28 (projectionelectrodes) (L1/L2=⅕-{fraction (1/10)}). More specifically, assumingthat the diameter L2 of the solder bumps 28 is 500 μm, the diameter L1of the contact pins 30 is set in the range of 100-50 μm. Thus, thediameter of the contact pins 30 is made to have a significantly smallerdiameter than the solder bumps 28.

[0082] The elastic member 31 for supporting the contact pins 30 may beformed of a material capable of elastic deformation such as a foamrubber, a foam glass or a styrene foam. The contact pins 30 are arrayedin the elastic member 31 so as to be aligned with the respective solderbumps 28. The contact pins 30 stand embedded in the elastic member 31such that the upper ends thereof are flush with an upper surface 31 a ofthe elastic member 31. Also, the lower ends of the contact pins 30 areflush with a lower surface 31 b of the elastic member 31.

[0083] By using the elastic member 31 and by supporting the contact pins30 by embedding the contact pins 30 in the elastic member 31, thecontact pins 30 are properly supported over the entirety thereof.

[0084] A description will now be given, primarily with reference toFIGS. 8 and 9, of the operation and function of the IC socket 20 havingthe above described construction. In FIGS. 8 and 9, illustration of thesocket body 21 and the lid 22 is omitted.

[0085]FIG. 8 shows a state before the IC 25 is mounted on the IC socket20. As shown in FIG. 8, the elastic member 31 is not deformed before theIC 25 is mounted on the IC socket 20, that is, when the IC 25 is removedfrom the contact unit 23. In this state, the contact pins 30 stand erectby being supported by the elastic member 31.

[0086] The IC 25 is mounted on the IC socket 20 such that the IC 25 isfirst placed on a predetermined mounting position on the contact unit 23(at which position the solder bumps 28 are aligned with thecorresponding contact pins 30). Subsequently, the lid 22 is closed andthe lock lever 29 is operated to lock the lid 22 in the closed position.The IC 25 mounted on the IC socket 20 is pressed hard toward the contactunit 23.

[0087] As described above, the contact pins 30 are formed of a materialwhich is harder than the material forming the solder bumps 28. Thediameter L1 of the contact pins 30 is configured to be ⅕-{fraction(1/10)} of the diameter L2 of the solder bumps 28. Accordingly, as theIC 25 is pressed toward the contact unit 23, upper ends 30 a of thecontact pins 30 pierce the solder bumps 28 as shown in FIG. 9.Accordingly, the contact pins 30 and the solder bumps 28 areelectrically connected to each other.

[0088] The IC socket 20 according to the first embodiment has thefollowing added effects compared to the IC socket having the basicconstruction.

[0089] Since the upper ends 30 a of the contact pins 30 are flush withthe upper surface 31 a of the elastic member 31, the contact pins 30pierce the solder bumps 28 so that the solder bumps 28 press the uppersurface 31 a of the elastic member 31. Since the elastic member 31 iselastically deformable, the elastic member is deformed elastically bybeing pressed by the solder bumps 28. Accordingly, the elastic member 31is prevented from blocking the electrical connection between the contactpins 30 and the solder bumps 28.

[0090] Even with their significantly small diameter, the contact pins 30are prevented from being bent or broken because the contact pins aresupported by the elastic member 31 constituting the contact unit 23.Therefore, the electrical connection with the solder bumps 28 can beproperly established.

[0091] A description will now be given of a second embodiment of thepresent invention.

[0092] FIGS. 10-12 show an IC socket 20A according to a secondembodiment of the present invention. In FIGS. 10-12, those componentsthat are the same as the components of the IC socket 20 according to thefirst embodiment described with reference to FIGS. 7-9 are designated bythe same reference numerals, and the description thereof is omitted.

[0093] In the IC socket 20 according to the first embodiment, thecontact pins 30 constituting the contact unit 23 are completely embeddedin the elastic member 31 so that only the ends of the contact pins 30are exposed in the upper surface 31 a and the lower surface 31 b of theelastic member 31. The solder bumps 28 are connected to the contact pins30 such that as the elastic member 31 is elastically deformed by thesolder bumps 28, the contact pins 30 pierce the solder bumps 28.

[0094] While the construction of the first embodiment ensures that thecontact pins 30 pierce the solder bumps 28, an elastic resilient forceproduced as the elastic member 31 is elastically deformed acts to removethe solder bumps 28 away from the contact pins 30. This action alsooccurs in the connection between the elastic member 31 and the testboard 32. Thus, the elastic member 31 may obstruct an electricconnection between the solder bumps 28 and the contact pins 30, andbetween the test board 32 and the contact pins 30.

[0095] An elastic member 31A of the second embodiment has portionsthereof in the vicinity of the ends of the contact pins 30 removed sothat the upper ends 30 a and the lower ends 30 b of the contact pins 30project from the surface of the elastic member 31A. The upper ends 30 aand the lower ends 30 b of the contact pins 30 may be caused to projectfrom the respective surfaces of the elastic member 31A by removing theupper surface 31 a and the lower surface 31 b of the elastic member 31to a certain depth or by performing a suitable mechanical or chemicalprocess.

[0096] By removing a portion of the upper surface 31 a and the lowersurface 31 b of the elastic member 31A so that the upper ends 30 a andthe lower ends 30 b of the contact pins 30 project from the elasticmember 31A, the elastic member 31 is prevented from obstructing aconnection between the solder bumps 28 and the contact pins 30 andbetween the test board 32 (the land part 33) and the contact pins 30.Thus, an electrical connection between the IC 25 and the IC socket 20Aand between the IC socket 20A and the test board 32 can be properlyestablished.

[0097] It is not necessary to reduce both the upper surface 31 a and thelower surface 31 b of the elastic member 31A in the vicinity of thecontact pins 30. Only one of the upper surface 31 a and the lowersurface 31 b may be reduced.

[0098] Another feature of the IC socket 20A according to the secondembodiment is that a positioning plate 36 is provided in the contactunit 23 in addition to the contact pins 30 and the elastic member 31A.The positioning plate 36 is formed of an insulating material such as aglass or a resin like polyimide.

[0099] The positioning plate 36 is provided on the upper surface of theelastic member 31A. The positioning plate 36 is provided with throughholes 35 that guide the contact pins 30 inserted therein and properlypositions the contact pins 30. The through holes 35 are aligned with thesolder bumps 28 of the IC 25. By inserting the contact pins 30 throughthe through holes 35, the contact pins 30 are positioned so as to bealigned with the solder bumps 28. The through holes 35 are formed in thebloc using, for example, etching technology because the through holes 35must be aligned with the solder bumps 28 with a high precision.

[0100] By providing the positioning plate 36, the contact pins 30 andthe solder bumps 28 can be properly positioned with respect to eachother when the IC 25 is mounted on the IC socket 20A.

[0101] The background for the second embodiment is that the upper ends30 a and the lower ends 30 b of the contact pins 30 may be displacedrelatively freely if the contact pins 30 are supported only by theelastic member 31A so that the contact pins 30 and the solder bumps 28may not be properly positioned with respect to each other when the IC 25is mounted on the IC socket 20A. The positioning plate 26 of the secondembodiment ensures that the contact pins 30 are properly positioned sothat the contact pins 30 and the solder bumps 28 are properly connectedto each other.

[0102] As shown in FIG. 11, an IC positioning part 37 (mountingpositioning part as claimed) for positioning the IC 25 properly isprovided in that part of the positioning plate 36 where the IC 25 ismounted. The IC 25 is properly positioned by its periphery engaging withthe IC positioning part 37. By merely mounting the IC 25 on the ICpositioning part 37, the IC 25 can be positioned in the IC socket 20Awith a high precision. Accordingly, an electrical connection between thecontact pins 30 and the solder bumps 28 can be properly established.

[0103] Positioning recesses 38 (electrode positioning part as claimed)for positioning the solder bumps 28 are formed on the upper surface ofthe positioning plate 36 shown in FIG. 11 so as to be opposite to thesolder bumps 28. The positioning recesses 38 are formed to be alignedwith the through holes 35. The positioning recesses 38 have a conicalconfiguration for proper engagement with corresponding portions of thegenerally spherical solder bumps 28.

[0104] When the IC 25 is mounted, the solder bumps 28 are properlypositioned by being engaged with the positioning recesses 38. As hasbeen described, since the positioning plate 36 also positions thecontact pins 30, the positioning of the contact pins 30 with respect tothe solder bumps 28 is performed with a high precision. Therefore, anelectrical connection between the solder bumps 28 and the contact pins30 can be properly established.

[0105] Conical guide recesses 39 for guiding the contact pins 30inserted therein are formed on the lower surface of the positioningplate 36 so as to be aligned with the through holes 35. The contact pins30 are guided by the guide recesses 39 and properly inserted in thethrough holes 35. A large number of contact pins 30 can be easilyinserted in the through holes 35 with a relatively small diameter sothat the mounting process can be performed efficiently.

[0106] A plating 40 formed of a conductive material is formed in theinner walls of the through holes 35 and the guide recesses 39 for properelectrical contact with the contact pins 30. The plating 40 is alsoformed in the positioning recesses 38 for proper electrical contact withthe solder bumps 28. Accordingly, the plating 40 serves to establish anelectrical connection between the contact pins 30 and the solder bumps28.

[0107] More specifically, the contact pins 30 come into contact with theplating 40 and are electrically connected therewith when inserted intothe through holes 35. Since the plating 40 is also formed in thepositioning recesses 38 which come into contact with the solder bumps28, the plating 40 is electrically connected to the solder bumps 28.Accordingly, the effective contact surface between the contact pins 30and the solder bumps 28 increases so that an electrical connectionbetween the contact pins 30 and the solder bumps 28 can be more properlyestablished.

[0108] A description will now be given of an alternative constructionwhich ensures a proper connection between the contact pins 30 and thesolder bumps 28.

[0109] In the construction shown in FIG. 13A, an insulating member 51provided with an IC positioning part 52 for positioning the IC 25 isformed in the elastic member 31 for supporting the contact pins 30. Theinsulating member 51 is formed of a resin (for example, a polyimideresin or the like) providing an electrical insulation. The ICpositioning part 52 formed in the insulating member 51 is a rectangularopening in which the IC 25 is mounted.

[0110] By mounting the IC 25 on the IC positioning part 52, the IC 25can be properly positioned with respect to the elastic member 31.Therefore, an electrical connection between the contact pins 30 and thesolder bumps 28 formed in the IC 25 can be properly established.

[0111] In the construction shown in FIG. 13B, the elastic member 31 isprovided with an insulating member 51A in which a bump positioning part53 is formed to accommodate the solder bumps 28 formed in the IC 25. Bypositioning the solder bumps 28 formed in the IC 25 so as to be fittedin the bump positioning part 53, the solder bumps 28 can be properlypositioned with respect to the elastic member 31. Therefore, anelectrical connection between the contact pins 30 and the solder bumps28 can be properly established.

[0112] In the construction shown in FIG. 14A, an IC positioning part 52Afor properly positioning the IC 25 is formed to be integral with theelastic member 31. The IC positioning part 52A may be formed byproviding, on the elastic member 31, a mask 54 having an opening alignedwith the IC mounting position so that a portion of the elastic member 31is removed using chemical etching. While the mask 54 is shown in FIG.14A, it is to be removed before the IC 25 is mounted on the ICpositioning part 52A.

[0113] Like the construction shown in FIG. 13A, the construction shownin FIG. 18A also ensures that the IC 25 can be properly positioned withrespect to the elastic member 31 just by mounting the IC 25 on the ICpositioning part 52A. Therefore, ah electrical connection between thecontact pins 30 provided in the elastic member 31 and the solder bumpsformed in the IC 25 can be properly established. Since the ICpositioning part 52A is formed to be integral with the elastic member31, the IC 25 can be positioned using a simple construction.

[0114] In the construction shown in FIG. 14B, a bump positioning part53A for positioning the bumps 28 is formed to be integral with theelastic member 31. By mounting the solder bumps 28 formed in the IC 25on the bump positioning part 53A, an electrical connection between thecontact pins 30 and the solder bumps 28 can be properly established.Since the bump positioning part 53A is formed to be integral with theelastic member 31, the solder bumps 28 can be positioned using a simpleconstruction.

[0115] A description will now be given of a third embodiment of thepresent invention.

[0116]FIG. 15 shows a portion of an IC socket 20B according to a thirdembodiment of the present invention. Illustration of the socket body 21and the lid 22 is omitted. In FIG. 15, those components that are thesame as the components of the IC socket 20 and 20A according to thefirst and second embodiments, respectively, are designated by the samereference numerals and the description thereof is omitted.

[0117] The IC socket 20B according to the third embodiment isconstructed such that an upper guide plate 41 and a lower guide plate 42are provided in a contact unit 23B to sandwich the elastic member 31Aprovided with the contact pins 30. The upper guide plate 41 and thelower guide plate 42 are provided with positioning holes 43 an 44,respectively, for positioning the contact pins 30. The contact pins 30are movably guided by the positioning holes 43 and 44.

[0118] In order to prevent a relative displacement (dislocation) of theupper guide plate 41 and the lower guide plate 42, a dislocationpreventing plate 45 is provided at the sides of the upper guide plate 41and the lower guide plate 42. The upper end of the dislocationpreventing plate 45 is fixed to the upper guide plate 41 and the lowerend of the dislocation preventing plate 45 is fixed to the lower guideplate 42. Accordingly, a dislocation of the upper guide plate 41 and thelower guide plate 42 is prevented.

[0119] The third embodiment shows that the contact unit may have a pairof guide plates provided to sandwich the elastic member 31A instead ofthe positioning plate of the second embodiment provided on the uppersurface of the elastic member 31A or instead of an alternative guideplate provided on the lower surface thereof. According to theconstruction of the third embodiment, the contact pins 30 are positionedat the upper and lower ends thereof so that an electrical connectionbetween the solder bumps 28 and the contact pins 30 and between the testboard 32 (the land part 33) and the contact pins 30 can be properlyestablished.

[0120]FIG. 16 is a bottom view of the lower guide plate 42 provided onthe lower surface of the elastic member 31A. As shown in FIG. 16,connection parts 46, land parts 47 and lead parts 48 are printed on thatsurface of the lower guide plate 42 that faces the test board 32. Theconnection parts 46 are electrically connected to the contact pins 30.For example, the connection parts 46 may be through hole electrodesformed in the positioning holes 44. Therefore, the connection parts 46are provided at the same pitch as the pitch of the contact pins 30 (andthe pitch of the solder bumps 28).

[0121] The land parts 47 may be formed at a pitch wider than the pitchof the connection parts 46 because the arrangement of the land parts 47is not determined by the arrangement of the contact pins 30. The leadparts 48 electrically connect the connection parts 46 and the land parts47.

[0122] Since the arrangement of the connection parts 46 is determined bythe arrangement of the contact pins 30, the pitch of the connectionparts 46 can not be enlarged. However, the lead parts 48 according tothe third embodiment for leading the connection parts 46 to the landparts 47 ensures that the pitch of the connection parts 46 is virtuallyenlarged so as to be equal to the pitch of the land parts 47.

[0123] Accordingly, as shown in FIG. 8, by providing the land parts 47with external connection terminals 49 for connection with the test board32, an electrical connection between the test board 32 and the IC socket20B can be easily and properly established.

[0124] A description will now be given of a fourth embodiment of thepresent invention.

[0125]FIGS. 17 and 18 are schematic views of an IC socket 20C accordingto the fourth embodiment. Illustration of the socket body 21 and the lid22 is omitted. In FIGS. 17 and 18, those components that are identicalto the components of the IC socket 20B according to the third embodimentshown in FIG. 15 are designated by the same reference numerals and thedescription thereof is omitted.

[0126] The feature of the IC socket 20C according to the thirdembodiment is that the contact pins 30 provided in a contact unit 23Care fixed to the upper guide plate 41 such that their heights from thesurface of the guide plate 41 are uniform. Referring to FIG. 17, thecontact pins 30 are made to have the regular height H from the surfaceof the upper guide plate 41. The contact pins 30 may be fixed to theupper guide plate 41 using, for example, an adhesive 50. By using theadhesive 50, the contact pins 30 and the upper guide plate 41 becomeintegral with each other. The contact pins 30 are not fixed to the lowerguide plate 42 provided on the lower surface of the elastic member 31A.The construction involving the contact pins 30 and the lower guide plate42 are the same as the corresponding construction according to the thirdembodiment.

[0127] As described above, by fixing the contact pins 30 to the upperguide plate 41, a variation in the height of the upper ends 30 a of thecontact pins 30 connected to the solder bumps 28 can be prevented.

[0128] A case is assumed in which the contact pins 30 are movable withrespect to the upper guide plate 41 (that is, assuming the constructionof the third embodiment), and in which the test board 23 is warped asshown in FIGS. 17 and 18. As described in the foregoing embodiments,since the lower ends 30 b of the contact pins 30 come into contact withthe test board 32 and are electrically connected thereto, a variation inthe height of the upper ends 30 a of the contact pins 30 conforming tothe configuration of the test board 32 occurs.

[0129] If a variation in the height of the upper ends 30 a of thecontact pins 30 occurs, the depth of the contact pins 30 piercing thesolder bumps 28 differs from pin to pin. Accordingly, a variation in theconductivity occurs and the test may not be successfully conducted.

[0130] By fixing the contact pins 30 to the upper guide plate 41 in auniform height from the surface of the upper guide plate 41 according tothe fourth embodiment, the upper ends 30 a of the contact pins 30 aremaintained at the uniform height H from the upper guide plate 41 evenwhen the test board 32 does not have a level surface due to a warp orthe like. Therefore, as shown in FIG. 18, the contact pins 30 pierce thesolder bumps 28 to the regular depth so that the electrical conductivitybetween the contact pins 30 and the solder bumps 28 is stabilized.

[0131] The contact pins 30 are inserted through the positioning holes 44of the lower guide plate 42 so as to be displaceable therein. Thecontact pins 30 and the elastic member 31A supporting the contact pins30 are elastically deformable. For this reason, even when the test board32 has a rugged surface due to a warp or the like, the contact pins 30and the elastic member 31A are elastically deformed below the upperguide plate 41. Accordingly, the contact pins 30 can be properlyconnected to the land parts 33 formed on the test board 32 when thecontact pins 30 are fixed to the upper guide plate 41 at the prescribedpositions thereof.

[0132] The depth to which the contact pins 30 pierce the solder bumps 28is determined by the height H of the contact pins 30 projecting abovethe upper guide plate 41. That is, when the solder bumps 28 come intocontact with the upper guide plate 41, the contact pins 30 do notpenetrate the solder bumps 28 further. In this way, it is possible toprevent the contact pins 30 from piercing the solder bumps 28 beyond arequired depth. Thus, the solder bumps 28 are prevented from beingdamaged and the main body of the IC 25 is prevented from being damagedby the contact pins 30 piercing the solder bumps 28.

[0133] While it is assumed that only the contact unit 23C is provided inthe IC socket 20C of the fourth embodiment described with reference toFIGS. 17 and 18, it is also possible to provide the positioning plate 36described with reference to FIGS. 10 and 11 in the IC socket 20C. Abenefit added to the fourth embodiment by providing the positioningplate 36 is that the IC 25 can be positioned with a higher precision andthe solder bumps 28 and the contact pins 30 are electrically connectedto each other more properly.

[0134] A description will now be given of an IC socket according to afifth embodiment.

[0135]FIG. 19 shows an IC socket 20D according to a fifth embodiment. InFIG. 15, those components that are identical to the components of the ICsocket 20B according to the third embodiment described with reference toFIG. 15 are designated by the same reference numerals and thedescription will be omitted.

[0136] The IC socket 20D according to the fifth embodiment differs fromthe IC socket 20B according to the third embodiment shown in FIG. 15 inthat the elastic member 31A and the dislocation preventing plate 45 areeliminated and the upper guide plate 41 and the lower guide plate 42 forsupporting the contact pins 30 are provided.

[0137] The upper guide plate 41 is provided with supporting holes 56 inwhich the contact pins 30 are inserted and adhesively fixed, and thelower guide plate 42 is provided with supporting holes 57 in which thecontact pins 30 are inserted. The upper guide plate 41 and the lowerguide plate 42 are spaced apart so as to reside near the upper ends andthe lower ends of the contact pins 30, respectively.

[0138] Therefore, only the contact pins 30 exist between the upper guideplate 41 and the lower guide plate 42. The contact pins 30 according tothe fifth embodiment are not supported by the elastic member and aremore easily displaced between the upper guide plate 41 and the lowerguide plate 42 than the contact pins 30 of the foregoing embodiments.

[0139] Assuming that the contact pins 30 are supported in such a mannerthat it is impossible or difficult for the contact pins 30 to bedisplaceable, a variation in the electrical connection between the thecontact pins 30 and the test board 32, and between the contact pins 30and the solder bumps 28 occurs if the height of the solder bumps 28formed on the IC 25 differs from bump to bump, or if the test board 32does not have a level surface due to a warp or the like. If there is avariation in the electrical connection, an associated variation in theelectrical conductivity occurs and the test may not be conductedproperly.

[0140] In the IC socket 20D according to the fifth embodiment, since thecontact pins 30 are easily displaceable between the upper guide plate 41and the lower guide plate 42, the elastic deformation of the contactpins 30 cancels the variation in the height of the solder bumps 28 andthe warp or the like of the test board 32. Accordingly, a properelectrical connection is established between the contact pins 30 and thesolder bumps 28, and between the contact pins 30 and the test board 32,resulting in a stabilized electrical conductivity.

[0141] A description will now be given, with reference to FIGS. 20A-23C,of configurations of the ends of the contact pins 30 connected to thesolder bumps 28 and the land parts 33 of the test board 32.

[0142] In the construction shown in FIGS. 20A and 20B, at least the endsof the contact pins 30 piercing the solder bumps 28 are formed as asharp edge. FIG. 20A shows a conical sharp edge 60 provided at the endof the contact pin 30. FIG. 20B shows a diagonally cut sharp edge 61 atthe end of the contact pin 30.

[0143] The conical sharp edge 60 and the diagonally cut sharp edge 61may be formed by grinding, chemically treating or diagonally cutting theend of the contact pin 30 exposed from the elastic member. By formingthe sharp edges 60 or the sharp edges 61 in the contact pins 30, it iseasy for the contact pins 30 to pierce the solder bumps 28 and thedamage caused in the solder bumps 28 can be reduced (the solder bumps 28are deformed to a smaller degree).

[0144] In the construction shown in FIG. 20C, the contact pins 30 areprovided with a plating 62 at its end. The plating 62 may be formed ofgold (Au) or the like characterized by a good conductivity. By formingthe plating 62 at the end of the contact pins 30, an electricalconductivity between the contact pins 30 and the solder bumps 28 piercedthereby can be improved.

[0145] While the contact pins 30 are configured to pierce the solderbumps 28 according to the foregoing embodiments, the contact pins 30shown in FIGS. 21C-23C are configured to establish an electricalconnection with the solder bumps 28 without piercing the solder bumps28.

[0146] The construction shown in FIGS. 21A and 21B features a spiralpart 63 formed at the end of the contact pins 30. The spiral part 63 isinherently displaceable in a longitudinal direction.

[0147] As shown in FIG. 21B, when the IC is mounted so that the solderbumps 28 formed thereon contact the spiral part 63, the solder bumps 28,characteristically formed of a soft material, are prevented from beingdamaged or deformed thanks to an elastic deformation of the spiral part63. Further, the spiral part 63 comes into contact with the solder bump28 at positions indicated by the circles drawn by the broken lines inFIG. 21B, which positions are removed from the lower end of the solderbump 28.

[0148] Since the lower end of the solder bump 28 is soldered to theboard to which the IC 25 is mounted, any damage or deformation in thelower end may prevent the mounting process from being performedproperly. By forming the spiral part 63 at the end of the contact pins30 so that the contact pins 30 do not come into contact the lower end ofthe solder bumps 28, the lower end of the solder bumps 28 is preventedfrom being damaged or deformed when the IC is tested.

[0149] In the construction shown in FIG. 22A, a randomly deformed part64 is formed at the end of the contact pins 30 by bending the end in arandom manner. By providing the randomly deformed part 64 at the end ofthe contact pins 30, the solder bumps 28 are encased in the randomlydeformed part 64 and remain in contact therewith while the IC is beingtested. The solder bumps 28, characteristically formed of a softmaterial, are prevented from being damaged or deformed, and anelectrical connection therewith can be properly established.

[0150] In the construction shown in FIG. 22B, a coil part 65 is producedat the end of the contact pins 30 so that the longitudinal direction ofthe coil part 65 is perpendicular to the longitudinal direction of thecontact pins 30. By forming the coil part 65 at the end of the contactpins 30, the coil part 65 is deformed according to the configuration ofthe solder bumps 28 when the solder bumps 28 are pressed against thecoil part 65 in testing the IC. Accordingly, the solder bumps 28 comeinto contact with the coil part 65 at a large number of points.Accordingly, an electrical connection between the solder bumps 28 andthe contact pins 30 can be properly established.

[0151] Any variation in the height of the solder bumps 28 or theirregularity on the surface of the test board 32 can be canceled by adeformation of the coil part 65. In this way, an electrical conductivitybetween the solder bumps 28 and the contact pins 30 can be improved.

[0152] In the construction shown in FIG. 23A, an arcuate part 66 isprovided at the end of the contact pins 30 by bending it into an arcuateconfiguration. The arcuate part 66 provides a spring action.

[0153] When the solder bump 28 presses the arcuate part 66 while the ICis being tested, the arcuate part 66 is deformed as illustrated in FIG.23A. Therefore, the force (exercised as a counter force of a pressureprovided by the lid 22 on the IC 25) against the solder bumps 28 can berelieved. Accordingly, the solder bumps 28 can be prevented from beingdamaged or deformed. Any variation in the height of the solder bumps 28and the irregularity on the surface of the test board 23 can becanceled.

[0154] In the construction shown in FIG. 23B, the end of the contact pin30 is bent to form a crooked part 67. The crooked part 67 formed at theend of the contact pins 30 provides the same function as the arcuatepart 66 shown in FIG. 23A. Accordingly, the solder bumps 28 can beprevented from being damaged or deformed. Any variation in the height ofthe solder bumps 28 and the irregularity on the surface of the testboard 23 can be canceled by the crooked part 67.

[0155] As has been described, by forming the spiral part 63, therandomly deformed part 64, the coil part 65, the arcuate part 66 or thecrooked part 67 at that portion of the contact pins 30 connected withthe solder bump 28 so that any of these parts comes into contact withthe solder bump 28 and is deformed accordingly, any variation in theheight of the solder bumps 28 and the irregularity on the surface of thetest board 23 can be canceled. Since the parts 63-67 are deformedaccording to the configuration of the solder bump 28, a relatively widecontact area is secured. Accordingly, an electrical conductivity betweenthe contact pins 30 and the solder bumps 28 can be improved.

[0156] Also, even if the material forming the solder bumps 28 is soft,the contact pins 30 and the solder bumps 28 can be electricallyconnected to each other without any damage being caused in the solderbumps 28 because the parts 63-67 are formed to be deformable.

[0157] In the construction shown in FIG. 23C, the contact pin 30 isprovided with a sharply-bent part 68 provided by bending the end of thecontact pin 30 piercing the solder bump 28 in a sharp angle.

[0158] The sharply bent part 68 formed at the end of the contact pin 30is bent in an even sharper angle when the contact pin 30 pierce thesolder bump 28 (that is, the sharply bent part 68 is deformed from thestate indicated by the broken line of FIG. 23C to the state indicated bythe solid line). The sharply bent part 68 that has pierced the solderbump 28 and is located therein presses the solder bump toward theperiphery of the solder bump 28, due to an elastic resilient force.Accordingly, an electrical connection between the contact pins 30 andthe solder bumps 28 can be properly established.

[0159] A description will now be given of the mounting mechanism formounting the IC sockets 20, 20A-20D on the test board 32.

[0160] FIGS. 24A-24C shows variations of the mounting mechanism. Themounting mechanisms shown in FIGS. 24A-24C have the same basicconstruction. In the construction shown in FIG. 24A, an elasticallydeformable part 71 is formed at that end of the contact pin 30 which isconnected to the test board 23. In the construction shown in FIG. 24B,an elastically deformable part 72 is formed at that end of the contactpin 30 which is connected to the test board 23. In the constructionshown in FIG. 24C, an elastically deformable part 73 is formed at thatend of the contact pin 30 which is connected to the test board 23. Thecontact pin 30 is pressed against a through hole 70 formed in the testboard 32 due to an elastic resilient force generated when theelastically deformable part 71 (72, 73) is inserted, so that anelectrical connection is properly established between the elasticallydeformable part 71 (72, 73) and the through hole 70.

[0161] More specifically, the elastically deformable part 71 shown inFIG. 24A is in the form of a sharp edged bend 71; the elasticallydeformable part 72 shown in FIG. 24B is in the form of a curve; and theelastically deformable part 73 shown in FIG. 24C is in the form of acoil.

[0162] The elastically deformable part 71 (72, 73) is fitted in thethrough hole 70 by first deforming them so that it is elongated in thelongitudinal direction and inserting it in the through hole 70 while theelongated state is maintained. Subsequently, the elastically deformablepart is relieved of the force applied to cause the elongateddeformation. Thus, the elastically deformable part 71 (72, 73) returnsto an original configuration due to an elastic resiliency inside thethrough hole 70. Due to this elastic resilient force, the elasticallydeformable part 71 (72, 73) presses itself against the inner wall of thethrough hole 70 and establishes an electrical connection therewith.

[0163] According to the above-described mounting mechanism for mountingthe IC socket 20, 20A-20D on the test board 32, an electrical connectionbetween the contact pins 30 and the test board 32 can be properlyestablished by a simple operation of inserting the elasticallydeformable parts 71 (72, 73) into the through hole 70. Since theelastically deformable part 71 (72, 73) presses the through hole 70 byan elastic resilient force while the electrical connection isestablished, an electrical conductivity between the contact pins 30 andthe test board 32 can be improved.

[0164] In the mounting mechanism shown in FIGS. 25A and 25B, the throughholes 70 are formed at a pitch P2 wider than the pitch P1 at which thesolder bumps 28 and the contact pins 30 are provided (P1<P2). As shownin FIG. 25A, the foot of the contact pins 30 projecting toward the testboard 32 through the elastic member 31 supporting the contact pins 30are configured to be long enough to reach the respective through holes70.

[0165] As shown in FIG. 25B, the contact pins 30 are electricallyconnected to the test board 32 such that the portions of the contactpins 30 projecting through the elastic member 31 are guided into therespective through holes 70 and connected thereto.

[0166] According to the mounting mechanism of FIGS. 25A and 25B, thepitch P2 of the through holes 70 is wider than the pitch P1 of thesolder bumps which may be relatively narrow. Therefore, forming of thethrough holes 70 becomes easier, and forming of the wiring pattern (notshown) provided on the test board 32 for connection with the throughholes 70 also becomes easier.

[0167] The present invention is not limited to the above-describedembodiments, and variations and modifications may be made withoutdeparting from the scope of the present invention.

What is claimed is:
 1. An IC socket mounted on a test board while in useand having a semiconductor device with projection electrodes mounted onsaid IC socket for testing, said IC socket is constructed such that adiameter of a plurality of straight contact pins having a first endelectrically connected to said test board and a second end thereofconnected to said projection electrodes is sufficiently small for eachof said plurality of contact pins to pierce said projection electrodes,said IC socket being electrically connected to said test board by saidfirst end of said plurality of contact pins piercing said projectionelectrodes.
 2. The IC socket as claimed in claim 1 , wherein thediameter of each of said plurality of contact pins is ⅕-{fraction(1/10)} of a diameter of said projection electrodes.
 3. The IC socket asclaimed in claim 1 , wherein said plurality of contact pins are arrangedsuch that each of said plurality of contact pins is aligned with acorresponding one of said projection electrodes.
 4. The IC socket asclaimed in claim 1 , wherein said plurality of contact pins are arrangedsuch that a plurality of contact pins are aligned with a correspondingone of said projection electrodes.
 5. The IC socket as claimed in claim1 , wherein a supporting structure for supporting said plurality ofcontact pins is provided, said plurality of contact pins projecting fromsaid supporting structure by a distance commensurate with a depth ofeach of said plurality of contact pins piercing the corresponding one ofsaid projection electrodes.
 6. The IC socket as claimed in claim 5 ,wherein said supporting structure and a main body of said IC socket areseparate from each other.
 7. The IC socket as claimed in claim 1 ,wherein said supporting structure is an elastic member and saidplurality of contact pins are supported by being embedded in saidelastic member.
 8. The IC socket as claimed in claim 7 , wherein saidelastic member is reduced at least at those portions in the vicinity ofone of the first and second ends of said plurality of contact pins sothat one of the first and second ends of said plurality of contact pinsare exposed on a surface of said elastic member.
 9. The IC socket asclaimed in claim 5 , wherein said supporting structure is provided withan insulating member in which a semiconductor device positioning partfor positioning said semiconductor device is provided.
 10. The IC socketas claimed in claim 5 , wherein said supporting structure is providedwith an insulating member in which a projection electrode positioningpart for positioning said projection electrodes is provided.
 11. The ICsocket as claimed in claim 5 , wherein said supporting structure isprovided with an integral semiconductor device positioning part forpositioning said semiconductor device.
 12. The IC socket as claimed inclaim 5 , wherein said supporting structure is provided with an integralprojection electrode positioning part for positioning said projectionelectrodes.
 13. The IC socket as claimed in claim 5 , wherein saidsupporting structure comprises: an elastic member in which saidplurality of contact pins are embedded; and a guide plate provided on atleast one of a upper major surface and a lower major surface of saidelastic member and provided with positioning holes in which saidplurality of contact pins are inserted and positioned.
 14. The IC socketas claimed in claim 13 , wherein said guide plate is provided on atleast the upper major surface of said elastic member and said pluralityof contact pins are secured to said guide plate so that said pluralityof contact pins are in a uniform height.
 15. The IC socket as claimed inclaim 1 , said IC socket is provided with a positioning plate providedwith a device positioning part for positioning said semiconductor deviceat an appropriate position, said positioning plate being provided withthrough holes for guiding said plurality of contact pins at positionsaligned with said projection electrodes.
 16. The IC socket as claimed inclaim 15 , wherein guide recesses for guiding said projection electrodesare provided in said through holes.
 17. The IC socket as claimed inclaim 15 , wherein guide recesses for guiding said plurality of contactpins are provided in said through holes.
 18. The IC socket as claimed inclaim 15 , wherein a plating formed of a conductive material is formedin said through holes at those positions which are in contact with saidplurality of contact pins and said projection electrodes.
 19. The ICsocket as claimed in claim 13 , wherein said guide plate is providedwith connection parts electrically connected with said plurality ofcontact pins, land parts provided at a pitch wider than a pitch of saidplurality of connection parts, and lead parts connecting said connectionparts and said land parts.
 20. The IC socket as claimed in claim 1 ,wherein at least the second end of each of said plurality of contactpins is formed as a sharp edge.
 21. The IC socket as claimed in claim 1, wherein at least the second end of each of said plurality of contactpins is formed as a sharp bend.
 22. The IC socket as claimed in claim 5, wherein said supporting structure is implemented by a pair of supportplates provided with supporting holes in which said plurality of contactpins are inserted and supported therein, said pair of support platesbeing spaced apart from each other so as to be near respective ends ofsaid plurality of contact pins.
 23. An IC socket mounted on a test boardwhile in use and having a semiconductor device with projectionelectrodes mounted on said IC socket for testing, said IC socketcomprising: a plurality of straight contact pins having a first endelectrically connected to said test board and a second end connected tosaid projection electrodes; and a supporting structure for supportingsaid plurality of contact pins, each of said plurality of contact pinsprovided at the second end with a deformable part deformable accordingto a pressure occurring between said contact pin and an associated oneof said projection electrodes.
 24. The IC socket as claimed in claim 23, wherein a supporting structure is provided separate from a main bodyof said IC socket, said supporting structure is provided by an elasticmember so that said plurality of contact pins are inserted into saidelastic member and supported therein.
 25. An IC socket mountingmechanism for mounting, on a test board, an IC socket comprising acontact unit having a plurality of straight contact pins forelectrically connecting the test board and projection electrodes of asemiconductor device and also having a supporting structure forsupporting said plurality of contact pins, the test board included insaid IC socket mounting mechanism being provided with through holes towhich said plurality of contact pins are electrically connected, andeach of said plurality of contact pins having one end thereof connectedto said test board and provided with an elastically deformable part sothat an elastic resilient force generated when said elasticallydeformable part is inserted in an associated one of said through holescauses said contact pin to be pressed against the through hole and toestablish an electrical connection therewith.
 26. An IC socket mountingmechanism for mounting, on a test board, an IC socket comprising acontact unit having a plurality of straight contact pins forelectrically connecting the test board and projection electrodes of asemiconductor device and also having a supporting structure forsupporting said plurality of contact pins, the test board included insaid IC socket mounting mechanism being provided with through holes at apitch greater than a pitch at which said projection electrodes arearranged, and each of said plurality of contact pins is configured to belong enough to extend from said supporting structure to reach anassociated one of said through holes formed in said test board.
 27. AnIC test system for testing a semiconductor device-mounted on an ICsocket which is mounted on a test board connected to a test device, saidIC socket being constructed such that a diameter of a plurality ofstraight pins having a first end electrically connected to said testboard and a second end thereof connected to said projection electrodesis sufficiently small for each of said plurality of contact pins topierce said projection electrodes, said IC socket being electricallyconnected to said test board by said first end of said plurality ofcontact pins piercing said projection electrodes.
 28. An IC test systemfor testing a semiconductor device mounted on an IC socket which ismounted on a test board connected to a test device, said IC socketcomprising: a plurality of straight contact pins having a first endelectrically connected to said test board and another end connected tosaid projection electrodes; and a supporting structure for supportingsaid plurality of contact pins, each of said plurality of contact pinsprovided at the second end with a deformable part deformable accordingto a pressure occurring between said contact pin and an associated oneof said projection electrodes.